This invention relates to pyrrolopyridazine derivatives or pharmaceutically acceptable salts thereof; to pharmaceutical compositions comprising a pyrrolopyridazine derivative or a pharmaceutically acceptable salt thereof (preferably compositions for the prevention or treatment of ulcerative disease) as an active ingredient; to the use of a pyrrolopyridazine derivative or a pharmaceutically acceptable salt thereof in the preparation of a pharmaceutical composition (preferably a composition for the prevention or treatment of ulcerative disease); or to a method for the prevention or treatment of disease (preferably ulcerative disease), which method comprises administering a pharmaceutically effective amount of a pyrrolopyridazine derivative or a pharmaceutically acceptable salt thereof to a warm-blooded animal (preferably a human).
It has been considered that an inbalance between aggressive factors and protective factors against the gastric mucous membrane induces peptic ulcers. Gastric acid secretion is an aggressive factor and suppression of gastric acid secretion is useful in the prevention and treatment of the disease. Anticholinergic agents, histamine H2 receptor antagonists such as cimetidine and the like and proton pump inhibitors such as omeprazole and the like have been clinically used as a gastric acid secretion inhibitor. Although these agents are excellent therapeutic agents for ulcerative disease, the disease may recur after cessation of the therapy. It has been recently reported that Helicobacter pylon relates to recurrence of the ulcerative disease. Actually there have been some attempts to use a gastric acid secretion inhibitor in combination with an antibacterial agent for treatment of the disease.
Accordingly a compound that exhibits potent gastric acid secretory inhibition activity, excellent gastric mucous membrane protection activity and potent antibacterial activity against Helicobacter pylori would be expected to be an excellent medicament (preferably a prophylactic and therapeutic agent for ulcerative disease).
Some pyrrolopyridazine derivatives that have gastric acid secretory inhibition activity and gastric mucous membrane protection activity have been known (for example, WO 91/17164, WO 92/06979, WO 93/08190 and the like). The activity against Helicobacter pylori of some pyrrolopyridazine derivatives has also been known (for example, Japanese Patent Application Publication Hei 7-247285 and the like).
The inventors have continued an investigation on the pharmacological activities of pyrrolopyridazine derivatives in order to discover a medicament (preferably an agent for ulcerative disease) that exhibits potent gastric acid secretory inhibition activity, protects gastric mucous membranes and has excellent antibacterial activity against Helicobacter pylori for a long time. As a result, they found that some pyrrolopyridazine derivatives substituted with specific substituents at the 3-position exhibit potent gastric acid secretory inhibition activity and gastric mucous membrane protection activity and exhibit excellent antibacterial activity against Helicobacter pylori. 
The pyrrolopyridazine derivative, i.e., compound, of the present invention has the following formula: 
wherein:
R1 represents a C2-C6 alkenyl group, a halogeno C2-C6 alkenyl group, a C3-C7 cycloalkyl group which may be optionally substituted with C1-C6 alkyl or a C3-C7 cycloalkyl-C1-C6 alkyl group which may be optionally substituted with C1-C6 alkyl; R2 represents a C1-C6 alkyl group;
R3 represents a hydroxymethyl group, a C2-C6 aliphatic acyloxymethyl group, a C6-C10 arylcarbonyloxymethyl group which may be optionally substituted with substituents selected from the group consisting of C1-C6 alkyl, C1-C6 alkoxy and halogeno, a C1-C6 alkoxycarbonyloxymethyl group, a formyl group, a carboxyl group, a C1-C6 alkoxycarbonyl group or a C6-C10 aryloxycarbonyl group which may be optionally substituted with substituents selected from the group consisting of C1-C6 alkyl, C1-C6 alkoxy and halogeno;
R4 represents a C6-C10 aryl group which may be optionally substituted with substituents selected from the group consisting of C1-C6 alkyl, halogeno C1-C6 alkyl, C1-C6 alkoxy, halogeno C1-C6 alkoxy and halogeno;
A represents an imino group, an oxygen atom or a sulfur atom;
In the formula (I) described above:
The C1-C6 alkyl group in the definition of R2 or the C1-C6 alkyl moiety included in the definition of R1, R3 or R4 is, for example, a methyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl t-butyl, pentyl or hexyl group; preferably a C1-C4 alkyl group; more preferably a methyl or ethyl group; and most preferably a methyl group.
The C2-C6 alkenyl group or C2-C6 alkenyl moiety of the halogeno C2-C6 alkenyl group in the definition of R1 is, for example, a vinyl, 1-propenyl, 2-propenyl, isopropenyl, 1-butenyl, 2-butenyl, 1-methyl-1-propenyl, 1-methyl-2-propenyl, 2-methyl-1-propenyl, 2-methyl-2-propenyl, 2-pentenyl or 2-hexenyl group; preferably a C2-C4 alkenyl group, more preferably a C3-C4 alkenyl group; still more preferably a 2-propenyl or 2-butenyl group; and most preferably a 2-butenyl group.
A typical example of a halogeno C2-C6 alkenyl group in the definition of R1 is, for example, a 2,2-difluorovinyl, 3-fluoro-2-propenyl, 3-chloro-2-propenyl, 3-bromo-2-propenyl, 3-iodo-2-propenyl, 3,3-difluoro-2-propenyl, 2,3-dichloro-2-propenyl, 3,3-dichloro-2-propenyl, 2,3-dibromo-2-propenyl, 3,3-dibromo-2-propenyl, 4,4,4-trifluoro-2-butenyl, 5-fluoro-2-pentenyl or 6-fluoro-2-hexenyl group; preferably a 3-chloro-2-propenyl, 3,3-difluoro-2-propenyl, 3,3-dichloro-2-propenyl or 4,4,4-trifluoro-2-butenyl group; and more preferably a 3-chloro-2-propenyl, 3,3-difluoro-2-propenyl or 3,3-dichloro-2-propenyl group.
The C3-C7 cycloalkyl moiety of the C3-C7 cycloalkyl group which may be optionally substituted with a C1-C6 alkyl group or of the C3-C7 cycloalkyl-C1-C6 alkyl group which may be optionally substituted with a C1-C6 alkyl group in the definition of R1 is, for example, a cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl or cycloheptyl group; preferably a C3-C6 cycloalkyl group; more preferably a cyclopropyl, cyclopentyl or cyclohexyl group; and most preferably a cyclopropyl group.
A typical example of the C3-C7 cycloalkyl group which may be optionally substituted with a C1-C6 alkyl group in the definition of R1 is, for example, a cyclopropyl, 2-ethylcyclopropyl, 2-thylcyclopropyl, 2-ropylcyclopropyl, 2-exylcyclopropyl, cyclobutyl, 2-methylcyclobutyl, cyclopentyl, 2-methylcyclopentyl, 2-ethylcyclopentyl, cyclohexyl, 2-methylcyclohexyl or cycloheptyl group; preferably a cyclopropyl, 2-methylcyclopropyl, 2-ethylcyclopropyl, cyclobutyl, cyclopentyl, 2-methylcyclopentyl, cyclohexyl or 2-methylcyclohexyl group; more preferably a cyclopropyl, 2-methylcyclopropyl, cyclopentyl, 2-methylcyclopentyl, cyclohexy or 2-methylcyclohexyl group; and most preferably a cyclopropyl or 2-methylcyclopropyl group.
A typical example of the C3-C7 cycloalkyl-C1-C-6 alkyl group which may be optionally substituted with a C1-C6 alkyl group in the definition of R1 is, for example, a cyclopropylmethyl, 2-cyclopropylethyl, 2-methylcyclopropylmethyl, 2-(2-methylcyclopropyl)ethyl, 3-(2-methylcyclopropyl)propyl, 6-(2-methylcyclopropyl)hexyl, 2-ethylcyclopropylmethyl, 2-propylcyclopropylmethyl, 2-hexylcyclopropylmethyl, cyclobutylmethyl, 2-methylcyclobutylmethyl, cyclopentylmethyl, 2-cyclopentylethyl, 2-methylcyclopentylmethyl, 2-(2-methylcyclopentyl)ethyl, 2-ethylcyclopentylmethyl, cyclohexylmethyl, 2-cyclohexylethyl, 2-methylcyclohexylmethyl, 2-(2-methylcyclohexyl)ethyl or cycloheptylmethyl group; preferably a cyclopropylmethyl, 2-cyclopropylethyl, 2-methylcyclopropylmethyl, 2-(2-methylcyclopropyl)ethyl, 2-ethylcyclopropylmethyl, cyclobutylmethyl, 2-methylcyclobutylmethyl, cyclopentylmethyl, 2-methylcyclopentylmethyl, cyclohexylmethyl or 2-methylcyclohexylmethyl group; more preferably a cyclopropylmethyl, 2-methylcyclopropylmethyl, 2-ethylcyclopropylmethyl, cyclobutylmethyl, 2-methylcyclobutylmethyl, cyclopentylmethyl or 2-methylcyclohexylmethyl group; more preferably a cyclopropylmethyl, 2-methylcyclopropylmethyl, cyclopentylmethyl or 2-methylcyclohexylmethyl group; still more preferably a cyclopropylmethyl or 2-methylcyclopropylmethyl group; and most preferably a 2-methylcyclopropylmethyl group.
The C2-C6 aliphatic acyl moiety of the C2-C6 aliphatic acyloxymethyl group in the definition of R3 is, for example, an acetyl, propionyl, butyryl, isobutyryl, valeryl, isovaleryl or hexanoyl group; preferably a C2-C4 aliphatic acyl group; more preferably a C2-C3 aliphatic acyl group; and most preferably an acetyl group.
The C1-C6 alkoxy moiety of a substituent of the aryl group or a C1-C6 alkoxy moiety of the halogeno C1-C6 alkoxy group of a substituent of the aryl group in the definition of R3 and R4 or the C1-C6 alkoxy moiety of the C1-C6 alkoxycarbonyloxymethyl group and the C1-C6 alkoxycarbonyl group in the definition of R3 is, for example, a methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, s-butoxy, t-butoxy, pentyloxy or hexyloxy group; preferably a C1-C4 alkoxy group; more preferably a methoxy or ethoxy group; and most preferably a methoxy group.
The halogen atom included in the definition of R1, R3 and R4 is, for example, a fluorine, chlorine, bromine or iodine atom; preferably a fluorine, chlorine or bromine atom; more preferably a fluorine or chlorine atom.
The C6-C10 aryl moiety of the optionally substituted C6-C10 aryl moiety in the definition of R3 or of the optionally substituted C6-C10 aryl group in the definition of R4 is, for example, a phenyl or naphthyl group; preferably a phenyl group.
The number of the substitutents on the aryl group is, for example from 1 to 5; preferably from 1 to 3; more preferably 1 or 2; and most preferably one.
The preferred C6-C10 aryl moiety which may be optionally substituted with substituents selected from the group consisting of C1-C6 alkyl, C1-C6 alkoxy and halogeno in the definition of R3 is, for example, a phenyl, methylphenyl, dimethylphenyl, methoxyphenyl, dimethoxyphenyl, fluorophenyl, chlorophenyl, bromophenyl, difluorophenyl, chlorofluorophenyl, dichlorophenyl, naphthyl, methylnaphtyl, methoxynaphthyl, fluoronaphthyl, chloronaphthyl or bromonaphthyl group; more preferably a phenyl, methylphenyl, methoxyphenyl, fluorophenyl or chlorophenyl group; most preferably a phenyl or methylphenyl group.
The preferred C6-C10 aryl group which may be optionally substituted with substituents selected from the group consisting of C1-C6 alkyl, halogeno C1-C6 alkyl, C1-C6 alkoxy, halogeno C1-C6 alkoxy, and halogeno in the definition of R4 is, for example, a phenyl, methylphenyl, trifluoromethylphenyl, methoxyphenyl, trifluoromethoxyphenyl, difluoromethoxyphenyl, fluorophenyl, chlorophenyl, bromophenyl, difluorophenyl, chlorofluorophenyl, dichlorophenyl, trifluorophenyl, trichlorophenyl, naphthyl, methylnaphtyl, methoxynaphthyl, fluoronaphthyl, chloronaphthyl or bromonaphthyl group; more preferably a phenyl, 4-methylphenyl, 4-trifluoromethylphenyl, 4-methoxyphenyl, 4-trifluoromethoxyphenyl, 4-difluoromethoxyphenyl, 2-, 3- or 4-fluorophenyl, 2-, 3- or 4-chlorophenyl, 4-bromophenyl, 2,4- or 2,6-difluorophenyl, 4-cloro-2-fluorophenyl, 2-chloro-4-fluorophenyl, 2,4- or 2,6-dichlorophenyl, 2,4,6-trifluorophenyl or 2,4,6-trichlorophenyl group; still more preferably a 4-fluorophenyl, 4-chlorophenyl, 2,4-difluorophenyl, 2,6-difluorophenyl, 4chloro-2-fluorophenyl, 2-chloro-4-fluorophenyl, 2,4-dichlorophenyl or 2,6-dichlorophenyl group; and most preferably a 4-fluorophenyl, 2,4-difluorophenyl or 4-chlorophenyl group.
The preferred group A is an oxygen atom or a sulfur atom; more preferably an oxygen atom.
The compound of formula (I) in this invention can exist as an optical isomer due to an asymmetric carbon atom(s) or as a geometrical isomer due to a double bond(s) or to ring structure. The present invention encompasses a single isomer and mixtures of such isomers.
The pharmaceutically acceptable salts of compounds of formula (I) are acid addition salts. Examples of such salt are, for example, a hydrohalogenic acid salt such as hydrofluoride, hydrochloride, hydrobromide, hydroiodide; a nitrate; a perchlorate; a sulfate; a phosphate; a carbonate; a C1-C6 alkylsulfonate which may be optionally substituted with fluorine atoms, such as methanesulfonate, trifluoromethanesulfonate, ethanesulfonate, pentafluoroethanesulfonate, propanesulfonate, butanesulfonate, pentanesulfonate, hexanesulfonate; a C6-C10 arylsulfonate such as benzenesulfonate, p-toluenesulfonate; a carboxylate such as acetate, propionate, lactate, benzoate, fumarate, maleate, succinate, citrate, tartrate, oxalate, malonate; or an amino acid salt such as glutamate or aspartate; preferably a hydrochloride, sulfate or carboxylate and most preferably a hydrochloride.
The compounds of formula (I) in this invention or salts thereof can exist as hydrates. The present invention encompasses such hydrates.
Preferred compounds of formula (I) are:
(1) a compound wherein R1 is a C2-C4 alkenyl group, a C3-C4 alkenyl group substituted with fluoro or chloro, a C3-C6 cycloalkyl group which may be optionally substituted with C1-C2 alkyl or a C3-C6 cycloalkyl-C1-C2 alkyl group which may be substituted with C1-C2 alkyl;
(2) a compound wherein R1 is a C3-C4 alkenyl group, a 3-chloro-2-propenyl group, a 3,3-difluoro-2-propenyl group, a 3,3-dichloro-2-propenyl group, a cyclopropyl group, a 2-methylcyclopropyl group, a 2-ethylcyclopropyl group, a cyclobutyl group, a cyclopentyl group, a 2-methylcyclopentyl group, a cyclohexyl group, a 2-methylcyclohexyl group, a cyclopropylmethyl group, a 2-methylcyclopropylmethyl group, a 2-ethylcyclopropylmethyl group, a cyclobutylmethyl group, a 2-methylcyclobutylmethyl group, a cyclopentylmethyl group or a 2-methylcyclohexylmethyl group;
(3) a compound wherein R1 is a 2-propenyl group, a 2-butenyl group, a cyclopropyl group, a 2-methylcyclopropyl group, a cyclopentyl group, a 2-methylcyclopentyl group, a cyclohexyl group, a 2-methylcyclohexyl group, a cyclopropylmethyl group, a 2-methylcyclopropylmethyl group, a cyclopentylmethyl group or a 2-methylcyclohexylmethyl group;
(4) a compound wherein R1 is a 2-propenyl group, a 2-butenyl group, a cyclopropyl group, a 2-methylcyclopropyl group, a cyclopropylmethyl group or a 2-methylcyclopropylmethyl group;
(5) a compound wherein R1 is a 2-butenyl group, a cyclopropylmethyl group or a 2-methylcyclopropylmethyl group;
(6) a compound wherein R2 is a C1-C4 alkyl group;
(7) a compound wherein R2 is a C1-C2 alkyl group;
(8) a compound wherein R2 is a methyl group;
(9) a compound wherein R3 is a hydroxymethyl group, a C2-C6 aliphatic acyloxymethyl group, a benzoyloxymethyl group which may be optionally substituted with methyl, methoxy, fluoro or chloro, a C1-C4 alkoxycarbonyloxymethyl group, a formyl group, a carboxyl group, a C1-C4 alkoxycarbonyl group or a phenyloxycarbonyl group which may be optionally substituted with methyl, methoxy, fluoro or chloro;
(10) a compound wherein R3 is a hydroxymethyl group, a C2-C6 aliphatic acyloxymethyl group, a benzoyloxymethyl group, a C1-C2 alkoxycarbonyloxymethyl group, a formyl group, a carboxyl group, a C1-C2 alkoxycarbonyl group or a phenyloxycarbonyl group;
(11) a compound wherein R3 is a hydroxymethyl group, a C2-C4 aliphatic acyloxymethyl group, a C1-C2 alkoxycarbonyloxymethyl group, a formyl group, a carboxyl group or a C1-C2 alkoxycarbonyl group;
(12) a compound wherein R3 is a hydroxymethyl group, a C2-C3 aliphatic acyloxymethyl group, a formyl group or a carboxyl group;
(13) a compound wherein R3 is a hydroxymethyl group or an acetoxymethyl group;
(14) a compound wherein R4 is a phenyl group which is substituted with 1 to 3 substituents selected from the group consisting of C1-C4 alkyl, halogeno C1-C4 alkyl, C1-C4 alkoxy, halogeno C1-C4 alkoxy, fluoro, chloro and bromo;
(15) a compound wherein R4 is a phenyl group which is substituted with 1 to 3 substituents selected from the group consisting of methyl, trifluoromethyl, methoxy, trifluoromethoxy, difluoromethoxy, fluoro, chloro and bromo;
(16) a compound wherein R4 is a phenyl group which is substituted at the position(s) selected from the group consisting of 2-, 4- and 6-position of the phenyl group with 1 or 2 substituents selected from the group consisting of fluoro and chloro;
(17) a compound wherein R4 is a phenyl group which is substituted at the 4-position, 2,4-positions or 2,6-positions of the phenyl group with 1 or 2 substituents selected from the group consisting of fluoro and chloro;
(18) a compound wherein A is an oxygen atom or a sufur atom; and
(19) a compound wherein A is an oxygen atom.
In each group of compounds (1)-(5), (6)-(8), (9)-(13), (14)-(17), or (18)-(19) described above, the larger the number of the compound is, the more preferable the compound, (similarly in the group of compounds (20)-(24) described below). Compounds wherein R1, R2, R3, R4 and A are optionally selected from groups of compounds (1)-(5), (6)-(8), (9)-(13), (14)-(17), and (18)-(19), respectively, are a preferable.
Such compounds are as follows for example:
(20) a compound wherein R1 is a C2-C4 alkenyl group, a C3-C4 alkenyl group substituted with fluoro or chloro, a C3-C6 cycloalkyl group which may be optionally substituted with C1-C2 alkyl or a C3-C6 cycloalkyl-C1-C2 alkyl group which may be substituted with C1-C2 alkyl,
R2 is a C1-C4 alkyl group,
R3 is a hydroxymethyl group, a C2-C6 aliphatic acyloxymethyl group, a benzoyloxymethyl group which may be optionally substituted with methyl, methoxy, fluoro or chloro, a C1-C4 alkoxycarbonyloxymethyl group, a formyl group, a carboxyl group, a C1-C4 alkoxycarbonyl group or a phenyloxycarbonyl group which may be optionally substituted with methyl, methoxy, fluoro or chloro,
R4 is a phenyl group which is substituted with 1 to 3 substituents selected from the group consisting of C1-C4 alkyl, halogeno C1-C4 alkyl, C1-C4 alkoxy, halogeno-C1-C4 alkoxy, fluoro, chloro and bromo,
A is an oxygen atom or a sufur atom;
(21) a compound wherein R1 is a C3-C4 alkenyl group, a 3-chloro-2-propenyl group, a 3,3-difluoro-2-propenyl, a 3,3-dichloro-2-propenyl group, a cyclopropyl group, a 2-methylcyclpropyl group, a 2-ethylcyclopropyl group, a cyclobutyl group, a cyclopentyl group, a 2-methylcyclopentyl group, a cyclohexyl group, a 2-methylcyclohexyl group, a cyclopropylmethyl group, a 2-methylcyclopropylmethyl group, a 2-ethylcyclopropylmethyl group, a cyclobutylmethyl group, a 2-methylcyclobutylmethyl group, a cyclopentylmethyl group or a 2-methylcyclohexylmethyl group,
R2 is a C1-C4 alkyl group,
R3 is a hydroxymethyl group, a C2-C6 aliphatic acyloxymethyl group, a benzoyloxymethyl group, a C1-C2 alkoxycarbonyloxymethyl group, a formyl group, a carboxyl group, a C1-C2 alkoxycarbonyl group or a phenyloxycarbonyl group,
R4 is a phenyl group which is substituted with 1 to 3 substituents selected from the group consisting of methyl, trifluoromethyl, methoxy, trifluoromethoxy, difluoromethoxy, fluoro, chloro and bromo,
A is an oxygen atom or a sulfur atom;
(22) a compound wherein R1 is a 2-propenyl group, a 2-butenyl group, a cyclopropyl group, a 2-methylcyclopropyl group, a cyclopentyl group, a 2-methylcyclopentyl group, a cyclohexyl group, a 2-methylcyclohexyl group, a cyclopropylmethyl group, a 2-methylcyclopropylmethyl group, a cyclopentylmethyl group or a 2-methylcyclohexylmethyl group,
R2 is a C1-C2 alkyl group,
R3 is a hydroxymethyl group, a C2-C4 aliphatic acyloxymethyl group, a C1-C2 alkoxycarbonyloxymethyl group, a formyl group, a carboxyl group or a C1-C2 alkoxycarbonyl group,
R4 is a phenyl group which is substituted at the position(s) selected from the group consisting of 2-, 4- and 6-position of the phenyl group with 1 or 2 substituents selected from the group consisting of fluoro and chloro,
A is an oxygen atom;
(23) a compound wherein R1 is a 2-propenyl group, a 2-butenyl group, a cyclopropyl group, a 2-methylcyclopropyl group, a cyclopropylmethyl group or a 2-methylcyclopropylmethyl group,
R2 is a C1-C2 alkyl group,
R3 is a hydroxymethyl group, a C2-C3 aliphatic acyloxymethyl group, a formyl group or a carboxyl group,
R4 is a phenyl group which is substituted at the position(s) selected from the group consisting of 2-, 4- and 6-position of the phenyl group with 1 or 2 substituents selected from the group consisting of fluoro and chloro,
A is an oxygen atom; and
(24) a compound wherein R1 is a 2-butenyl group, a cyclopropylmethyl group of a 2-methylcyclopropylmethyl group
R2 is a methyl group,
R3 is a hydroxymethyl group or an acetoxymethyl group,
R4 is a phenyl group which is substituted at the 4position, 2,4-positions or, 2,6-positions of the phenyl group with 1 or 2 substituents selected from the group consisting of fluoro and chloro,
A is an oxygen atom.
Preferred compounds of formula (I) can be exemplified in Table 1.
Throughout the table 1 the following abbreviations are used with the following meanings.
Exemp. Comp. No.: Exemplification compound number,
Ac: acetyl, Bu: butyl, BUc: cyclobutyl, Bur: butyryl,
Et: ethyl, Hxc: cyclohexyl, Me: methyl, Pnc: cyclopentyl
Ph: phenyl, Pr: propyl, Prp : propionyl, Prc: cyclopropyl.
In Table 1, preferred compounds are the compounds of Exemplification Compound numbers 2,4, 8, 9, 17, 19, 20, 21, 22, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 56, 59, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 82, 90, 93, 95, 105, 106, 114, 116, 120, 121, 129, 132, 134, 138, 140, 142, 144, 146, 167, 178, 188, 192, 196, 200, 216, 225, 233, 237, 241, 245, 264, 277, 286, 290, 294, 298, 306, 307, 310, 311, 317, 323, 326, 329, 332, 345, 351, 357, 360, 363, 366, 373, 377, 381, 383, 385, 387, 394, 411, 414, 415, 416, 417, 418, 419, 420,421, 422, 423, 424, 425, 426, 427, 430, 433, 436, 439, 442, 449, 450, 451, 452, 453, 454, 455, 456, 457, 458, 461, 467, 470, 473, 476, 478, 480, 481, 482, 483, 484, 485, 486, 487, 488, 492, 494, 496, 498, 503, 504, 505, 506, 507, 508, 512, 514, 516, 518, 539, 542, 548, 558, 562, 564, 566, 583, 585, 589, 592, 594, 595, 596, 597, 598, 600, 602, 604, 606, 607, 608, 625, 626, 627, 633, 634, 665, 666, 667, 668, 669, 670, 671, 672, 675, 676, 681, 682, 683, 684, 685, 686, 702, 703, 704, 705, 706, 707, 723, 724, 725, 726, 727, 728, 834, 846, 858, 862, 889, 901, 930, 939, 990, 1014, 1018, 1072, 1090, 1094, 1113, 1117, 1133, 1136, 1148, 1149, 1159, 1163, 1164, 1165, 1167, 1169, 1171, 1173, 1175, 1177, 1181, 1185, 1189 and 1193.
More preferred compounds are the compounds of Exemplification Compound numbers 9, 19, 20, 22, 25, 32, 33, 40, 41, 43, 47, 48, 59, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 82, 93, 95, 105, 106, 114, 116, 120, 121, 134, 138, 142, 146, 167, 178, 311, 317, 416, 417, 420, 421, 427, 436, 439, 442, 450, 451, 454, 455, 461, 485, 506, 508, 589, 592, 594, 595, 596, 602, 606, 625, 633, 665, 666, 681, 682, 834, 846, 889, 1090, 1113, 1133, 1163, 1164, 1165, 1167, 1169, 1171, 1173, 1175 and 1177.
Further more preferred compounds are the compounds of Exemplification Compound numbers 9, 20, 22, 32, 33, 41, 43, 47, 48, 61, 63, 65, 69, 71, 73, 95, 106, 121, 421, 427, 455, 589, 594, 602, 606, 625, 1165 and 1169.
Still more preferred compounds are the compounds of Exemplification Compound numbers 22, 33, 43, 48, 106, 121, 421, 455 and 594.
Most preferred compounds are the compounds of:
Exemplification compound number 22: 1-(2-butenyl)-7-(4-fluorobenzyloxy)-3-hydroxymethyl-2-methylpyrrolo[2,3-d]pyridazine,
Exemplification compound number 33: 7-(4fluorobenzyloxy)-3-hydroxymethyl-2-methyl-1-(2-methylcyclopropylmethyl)pyrrolo[2,3-d]pyridazine,
Exemplification compound number 43: 1-(2-butenyl)-7-(2,4difluorobenzyloxy)-3-hydroxymethyl-2-methylpyrrolo[2,3-d]pyridazine,
Exemplification compound number 48: 7-(2,4-difluorobenzyloxy)-3-hydroxymethyl-2-methyl-1-(2-methylcyclopropylmethyl)pyrrolo[2,3-d]py-ridazine,
Exemplification compound number 106: 3-acetoxymethyl-7-4fluorobenzyloxy)-2-methyl-1-(2-methylcyclopropylmethyl)pyrrolo[2,3-d]pyridazine, and
Exemplification compound number 121: 3-acetoxymethyl-7-(2,4difluorobenzyloxy)-2-methyl-1-(2-methylcyclopropylmethyl)pyrrolo[2,3-d]pyridazine.
In addition, of the compounds described above, 1-[(1S,2S)-2-methylcyclopropylmethyl] derivatives are preferred compounds.
The pyrrolopyridazine compounds of formula (I) can be prepared according to the following method. 
In the above reaction scheme R1, R2, R4 and A have the same meanings as described above.
The step 1 is a process preparing a compound of formula (Ia) and is accomplished by reaction of a compound of formula (II) with an oxidizing agent in an inert solvent.
The oxidizing agent employed is, for example, an oxidizing agent by which a methyl group can be converted into a hydroxymethyl group, such as ammonium cerium (IV) nitrate, manganese (III) acetate or selenium dioxide; preferably ammonium cerium (IV) nitrate. The amount of the oxidizing agent is from 1.5 to 10 (preferably 2 to 6) moles to one mole of the compound of formula (II).
The employed inert solvent is not particularly limited provided that it has no adverse effect on the reaction and can dissolve the starting materials to a certain extent. Such a solvent is, for example, a halogeno-hydrocarbon such as methylene chloride, chloroform, carbon tetrachloride, dichloroethane, chlorobenzene, or dichlorobenzene; an ether such as diethyl ether, diisopropyl ether, tetrahydrofuran, dioxane, dimethoxyethane, or diethylene glycol dimethyl ether; a carboxylic acid or a carboxylic acid anhydride such as acetic acid, acetic anhydride, propionic acid, or benzoic acid; water; or mixtures thereof; and is preferably a carboxylic acid, a carboxylic acid anhydride, a carboxylic acid containing water or a mixture of a carboxylic acid and a carboxylic acid anhydride; and is more preferably acetic acid, acetic anhydride, acetic acid containing water or a mixture of acetic acid and acetic anhydride.
The reaction temperature is usually from 0xc2x0 C. to 150xc2x0 C. (preferably from room temperature to 100xc2x0 C.). The reaction time varies depending on the reaction temperature and other factors but it is from 30 minutes to 20 hours (preferably from 1 hour to 10 hours).
When a carboxylic acid or a carboxylic acid anhydride is used as the inert solvent in the step 1, in certain cases a product esterified at the hydroxymethyl group of compound (Ia) by the carboxylic acid can be obtained. The esterified compound is hydrolyzed according to a conventional method to give the compound of formula (Ia). For example the esterified compound is treated with a base (for example an alkali metal hydroxide such as lithium hydroxide, sodium hydroxide, or potassium hydroxide; or an alkali metal carbonate such as sodium carbonate, potassium carbonate; preferably an alkali metal hydroxide and most preferably lithium hydroxide) at from 0xc2x0 C. to 100xc2x0 C. (preferably from 10xc2x0 C. to 50xc2x0 C.) for from 10 minutes to 10 hours (preferably from 20 minutes to 5 hours) in an inert solvent containing water (for example, an alcohol containing water such as methanol containing water or ethanol containing water) to give a compound of formula (Ia).
A compound of formula (Id), which is a compound of formula (I) wherein R3 is a C2-C6 aliphatic acyloxymethyl group, a C6-C10arylcarbonyloxymethyl group which may be optionally substituted with substituents selected from the group consisting of C1-C6 alkyl, C1-C6 alkoxy and halogeno, or a C1-C6 alkoxycarbonyloxymethyl group, can be prepared by acylation of a compound of formula (Ia). 
In the formula of (Id), R5 represents a C2-C6 aliphatic acyl group, a C6-C10 arylcarbonyl group which may be optionally substituted with substituents selected from the group consisting of C1-C6 alkyl, C1-C6 alkoxy and halogeno, or a C1-C6 alkoxycarbonyl group, and R1, R2, R4 and A have the same meanings as described above.
The acylating reagent is, for example, a C2-C6 aliphatic acyl halide such as acetyl chloride, acetyl bromide, propionyl chloride, propionyl bromide, butyryl chloride, isobutyryl chloride, valeryl chloride, or hexanoyl chloride; a C2-C6 aliphatic carboxylic acid anhydride such as acetic anhydride, propionic anhydride, or hexanoic anhydride; a C6-C10 arylcarbonyl halide which may be optionally substituted with substituents selected from the group consisting of C1-C6 alkyl, C1-C6 alkoxy and halogeno, such as benzoyl chloride, benzoyl bromide, toluoyl chloride, toluoyl bromide, methoxybenzoyl chloride, chlorobenzoyl chloride, fluorobenzoyl chloride, or naphthoyl chloride; or a C1-C6 alkoxycarbonyl halide such as methoxycarbonyl chloride, ethoxycarbonyl chloride, ethoxycarbonyl bromide, propoxycarbonyl chloride, butoxycarbonyl chloride, pentyloxycarbonyl chloride, or hexyloxycarbonyl chloride; preferably a C2-C6 aliphatic acyl chloride, a C6-C10 arylcarbonyl chloride which may be optionally substituted with substituents selected from the group consisting of C1-C6 alkyl C1-C6 alkoxy and halogeno or a C1-C6 alkoxycarbonyl chloride.
The employed base is, for example, an alkali metal amide such as lithium amide, sodium amide, or potassium amide; an alkali metal carbonate such as lithium carbonate, sodium carbonate, or potassium carbonate; an alkali metal alkoxide such as lithium methoxide, sodium methoxide, sodium ethoxide, or potassium t-butoxide; or an organic amine such as triethylamine, tributylamine, diisopropylethylamine, N-ethylmorpholine, pyridine, picoline, 4-(N,N-dimethylamino)pyridine, quinoline, N,N-dimethylaniline, N,N-diethylaniline, 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), 1,4-diazabicyclo[2.2.2]octane (DABCO), or 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU); preferably an organic amine and most preferably triethylamine or pyridine.
The employed inert solvent is not particularly limited provided that it has no adverse effect on the reaction and can dissolve the starting materials to a certain extent. Such a solvent is, for example, an aromatic hydrocarbon such as benzene, toluene, or xylene; a halogeno-hydrocarbon such as methylene chloride, chloroform, carbon tetrachloride, dichloroethane, chlorobenzene, or dichlorobenzene; an ether such as diethyl ether, diisopropyl ether, tetrahydrofuran, dioxane, dimethoxyethane, or diethylene glycol dimethyl ether-, or mixtures thereof; and is preferably a halogeno-hydrocarbon or an ether; and is more preferably methylene chloride, chloroform, diethyl ether or tetrahydrofuran.
The reaction temperature is usually from 0xc2x0 C. to 100xc2x0 C. (preferably from 10xc2x0 C. to 50xc2x0 C.). The reaction time varies depending on the reaction temperature and other factors but it is from 10 minutes to 100 hours (preferably from 30 minutes to 5 hours).
The step 2 is a process for preparing a compound of formula (Ib) and is accomplished by reaction of a compound of formula (Ia) with an oxidizing agent in an inert solvent.
The employed oxidizing agent is, for example, an oxidizing agent by which a hydroxymethyl group can be converted into a formyl group, such as manganese dioxide, pyridinium chlorochromate (PCC), pyridinium dichromate (PDC), or a mixture of dimethyl sulfoxide and an acid anhydride (for example an aliphatic carboxylic acid anhydride which may be optionally substituted with halogeno, such as acetic anhydride, trifluoroacetic anhydride, or propionic anhydride; preferably acetic anhydride or trifluoroacetic anhydride); preferably manganese dioxide. The amount of the oxidizing agent is usually from 1 to 50 (preferably 2 to 30) moles to one mole of the compound of formula (Ia).
The employed inert solvent is not particularly limited provided that it has no adverse effect on the reaction and can dissolve the starting materials to a certain extent. Such a solvent is, for example, an aromatic hydrocarbon such as benzene, toluene, or xylene; a halogeno-hydrocarbon such as methylene chloride, chloroform, carbon tetrachloride, dichloroethane, chlorobenzene, or dichlorobenzene; an ether such as diethyl ether, diisopropyl ether, tetrahydrofuran, dioxane, dimethoxyethane, or diethylene glycol dimethyl ether; or mixtures thereof; and is preferably a halogeno-hydrocarbon; and is most preferably methylene chloride.
The reaction temperature is usually from 0xc2x0 C. to 150xc2x0 C. (preferably from room temperature to 100xc2x0 C.). The reaction time varies depending on the reaction temperature and other factors but it is from 30 minutes to 40 hours (preferably from 1 hour to 20 hours).
The step 3 is a process preparing a compound of formula (Ic) and is accomplished by reaction of a compound of formula (Ib) with an oxidizing agent in an inert solvent.
The employed oxidizing agent is, for example, an oxidizing agent by which a formyl group can be converted into a carboxyl group, such as silver oxide, pyridinium chlorochromate (PCC), or pyridinium dichromate (PDC); preferably silver oxide. The amount of the oxidizing agent is usually from 1 to 20 (preferably 2 to 10) moles to one mole of the compound of formula (Ib). When silver oxide is used as an oxidizing agent, silver oxide prepared by reaction of silver nitrate with an alkali metal hydroxide (preferably sodium hydroxide) is preferably used.
The employed inert solvent is not particularly limited provided that it has no adverse effect on the reaction and can dissolve the starting materials to a certain extent. Such a solvent is, for example, a halogeno-hydrocarbon such as methylene chloride, chloroform, carbon tetrachloride, dichloroethane, chlorobenzene, or dichlorobenzene; an ether such as diethyl ether, diisopropyl ether, tetrahydrofuran, dioxane, dimethoxyethane, or diethylene glycol dimethyl ether; an alcohol such as methanol, or ethanol; a carboxylic acid such as acetic acid, propionic acid, or benzoic acid; water; or mixtures thereof; and is preferably an alcohol, an alchohol containing water, a carboxylic acid, a carboxylic acid containing water or water; and is more preferably an alcohol containing water; and is most preferably ethanol containing water.
The reaction temperature is usually from 0xc2x0 C. to 150xc2x0 C. (preferably from room temperature to 100xc2x0 C.). The reaction time varies depending on the reaction temperature and other factors but it is from 1 hour to 72 hours (preferably from 12 hours to 48 hours).
A compound of formula (Ie), which is a compound of formula (I) wherein R3 is a C1-C6 alkoxycarbonyl group or a C6-C10 aryloxycarbonyl group which may be optionally substituted with substituents selected from the group consisting of C1-C6 alkyl, C1-C6 alkoxy and halogeno, can be prepared by esterification of a compound of formula (Ic). 
In the formula (Ie), R6 represents a C1-C6 alkyl group, or a C6-C10 aryl group which may be optionally substituted with substituents selected from the group consisting of C1-C6 alkyl, C1-C6 alkoxy and halogeno and R1, R2, R4 and A have the same meanings as described above.
The esterification is accomplished by reaction of a compound of formula (Ic) with a halogenating agent in an inert solvent to afford a carboxylic acid halide, followed by reaction of the carboxylic acid halide with an alcohol or a phenol derivative in the presence of a base in an inert solvent. The two step reactions can be carried out in a single reaction vessel, wherein the compound of formula (Ic) is reacted with a halogenating agent and, if necessary, the solvent can be removed from the reaction mixture.
The halogenating agent employed is, for example, a thionyl halide such as thionyl chloride, thionyl bromide or a phosphorus halide such as phosphorus trichloride, phosphorus pentachloride, phosphorus oxychloride, or phosphorus oxybromide; preferably thionyl chloride or phosphorus oxychloride.
The inert solvent employed in the reaction of the compound of formula (Ic) with a halogenating agent is not particularly limited provided that it has no adverse effect on the reaction and can dissolve the starting materials to a certain extent. Such a solvent is, for example, an aromatic hydrocarbon such as benzene, toluene, or xylene; a halogeno-hydrocarbon such as methylene chloride, chloroform, carbon tetrachloride, dichloroethane, chlorobenzene, or dichlorobenzene; an ether such as diethyl ether, diisopropyl ether, tetrahydrofuran, dioxane, dimethoxyethane, or diethylene glycol dimethyl ether; or mixtures thereof; and is preferably an ether; and is most preferably diethyl ether or tetrahydrofuran.
The reaction temperature is usually from 0xc2x0 C. to 100xc2x0 C. (preferably 10xc2x0 C. to 50xc2x0 C.). The reaction time varies depending on the reaction temperature and other factors but it is from 10 minutes to 10 hours (preferably from 30 minutes to 5 hours).
The inert solvent employed in the reaction of the carboxylic acid halide with an alcohol or phenol derivative is the same solvent as described in the reaction of the compound of formula (Ic) with a halogenating agent. The reaction temperature and the time required for the reaction are in the same range as described in the reaction of the compound of formula (Ic) with a halogenating agent.
In each step described above each desired compound may be isolated by conventional procedures from the reaction mixture. For example, it may be obtained 1) by filtration of the reaction mixture when insoluble material exists in the reaction mixture, followed by evaporation of the solvent of the filtrate; or by 1) concentration of the reaction mixture, 2) addition of water to the residue followed by partition between water and an appropriate organic solvent immiscible with water, 3) drying the extract over anhydrous magnesium sulfate and the like, followed by 4) concentration of the extract. The desired compound can be, if necessary, be further purified by conventional procedures such as recrystallization, column chromatography and the like.
A compound of formula (I) can be transformed into a pharmaceutically acceptable salt thereof by treatment of the compound of formula (I) with an acid according to a conventional technique. For example the desired salt can be obtained by reaction of a compound of formula (I) with an acid in an inert solvent (preferably an ether such as diethyl ether, tetrahydrofuran, or dioxane; an alcohol such as methanol, ethanol, or propanol; or a halogeno-hydrocarbon such as methylene chloride, or chloroform) at room temperature for from 5 minutes to 1 hour, followed by evaporation of the solvent.
The starting compound of formula (II) is known or can easily be prepared by the reaction of a pyrrole compound of formula (III) with a compound of formula R1-X (IV) according to a known method (for example Japanese Patent Application Publication Hei 7-247285); 
wherein R7 represents a C1-C6 alkyl group, R2 has the same meanings as described above, X represents a halogen atom (preferably a chlorine or bromine atom), and R1 has the same meanings as described above.
The compounds of formula (III) and (IV) are also known or can easily be obtained by a known procedure (for example Japanese Patent Application Publication Hei 7-247825; Monatschefte fur Chemie (1973), 104, 925; J. Chem. Soc., Perkin.Trans.II (1979) 287 and the like).
In addition each desired optically active compound of formula (I) and (IV) (for example 1S,2S-form) can be obtained by optical resolution of a racemic form of the corresponding compound (a mixture of 1S,2S-form and IR,2R-form and the like). The optical resolution can be carried out by an appropriate selection from conventional techniques such as chromatography on a column for optical resolution, preferential crystallization, and resolution of a mixture of diastereomeric salts.
The compounds of formula (I) or pharmaceutically acceptable salts thereof of this invention exhibit potent gastric acid secretion inhibition activity, gastric mucous membrane protection activity and potent antibacterial activity against Helicobacter pylori and they have excellent properties as a medicament. The compounds of formula (I) or pharmaceutically acceptable salts thereof are useful as a prophylactic or therapeutic medicament for the prevention and treatment of ulcerative diseases such as peptic ulcer, acute or chronic gastric ulcer, gastrisis, reflux esophagitis, gastroesophageal reflux disorder, dyspepsia, gastric hyperacidity, Zollinger-Ellison syndrome etc. and for bacterial infections arising from Helicobacter pylori. 
When used as a prophylactic or therapeutic medicament for the diseases described above, a compound of formula (I) or a pharmaceutically acceptable salt thereof (the active ingredient) can be administered alone or can be presented as part of a pharmaceutical formulation. The pharmaceutical formulation is prepared by blending the active ingredient with appropriate pharmaceutically acceptable carriers, e.g., excipients, diluents and the like, followed by formulation in the form of tablets, capsules, granules, powders or syrups and the like for oral administration or in the form of injections and the like for parenteral administration (preferably oral administration).
The production of such pharmaceutical formulations is carried out according to general techniques known to those skilled in the art using carriers which may includes such additives as an excipient, a binder, a disintegrant, a lubricant, a stabilizer, a corrigent, a diluent and a solvent for injections.
The excipient is, for example, a sugar derivative such as lactose, sucrose, glucose, mannitol, or sorbitol; a starch derivative such as corn starch, potato starch, xcex1-starch, dextrin, or carboxymethyl starch; a cellulose derivative such as crystalline cellulose, low-substituted hydroxypropyl cellulose, hydroxypropylmethyl cellulose, carboxymethyl cellulose, calcium carboxymethyl cellulose, or internally bridged sodium carboxymethyl cellulose; acacia; dextran; pullulan; a silicate derivative such as light silicic acid anhydride, synthetic aluminium silicate, or magnesium aluminate meta-silicate; a phosphonate derivative such as calcium phosphonate; a carbonate derivative such as calcium carbonate; a sulfate derivative such as calcium sulfate; and the like.
The binder is, for example, one of the excipients described above; gelatin; polyvinylpyrrolidone; macrogol (trade mark) and the like.
The disintegrant is, for example, one of the excipients described above; a chemically modified starch or cellulose derivative such as sodium croscarmellose or sodium carboxymethyl starch; bridged polyvinylpyrrolidone; and the like.
The lubricant is, for example, talc; stearic acid; a metal salt of stearic acid such as calcium stearate, or magnesium stearate; colloidal silica; a wax such as bee gum and spermaceti; boric acid; glycol; a carboxylic acid such as fumaric acid, or adipic acid; a sodium carboxylate such as sodium benzoate; a sulfate such as sodium sulfate; leucine; a laurylsulfate such as sodium laurylsulfate, or magnesium laurylsulfate; a silicic acid such as silicic acid anhydride, or a silicic acid hydrate; one of the starch derivatives described above in relation to the excipients; and the like.
The stabilizer is, for example, a p-hydroxybenzoate derivative such as methylparaben, or propylparaben; an alcohol such as chlorobutanol, benzyl alcohol, or phenylethyl alcohol; benzalkonium chloride; a phenol derivative such as phenol, or cresol; thimerosal; dehydroacetic acid; sorbic acid; and the like.
The corrigent is, for example, a sweetening, souring, or flavoring agent, which are conventionally used; and the like.
The solvent for injection is, for example, water, ethanol, glycerin and the like.
Suitable dosage levels will depend on the condition of the patient, human or other animal, the disease, whether the drug administration is for prevention or treatment, the age of the patient and the like, but typically suitable dosage levels for an active ingredient of the present invention are from 1 mg (preferably 5 mg) to 1000 mg (preferably 500 mg) for oral administration and from 0.1 mg (preferably 1 mg) to 500 mg (preferably 300 mg) for intravenous administration per unit dose, per day, for an adult human, respectively. The dosages described above are preferably administered from one time to six times throughout the day, depending on the condition of the disease.
The following Examples, Reference Examples, Test Examples and Formulation Examples are intended to further illustrate the present invention and are not intended to limit the scope of the invention.